# std::basic_string_view<CharT,Traits>::starts_with

From cppreference.com
< cpp‎ | string‎ | basic string view

constexpr bool starts_with( basic_string_view sv ) const noexcept; | (1) | (since C++20)
constexpr bool starts_with( CharT ch ) const noexcept; | (2) | (since C++20)
constexpr bool starts_with( const CharT* s ) const; | (3) | (since C++20)

Checks if the string view begins with the given prefix, where

1) the prefix is a string view. Effectively returns basic_string_view(data(), std::min(size(), sv.size())) == sv.
2) the prefix is a single character. Effectively returns !empty() && Traits::eq(front(), ch).
3) the prefix is a null-terminated character string. Effectively returns starts_with(basic_string_view(s)).

### Parameters

sv | - | a string view which may be a result of implicit conversion from `std::basic_string`
ch | - | a single character
s | - | a null-terminated character string

### Return value

true if the string view begins with the provided prefix, false otherwise.

### Notes

Feature-test macro | Value | Std | Feature
--- | --- | --- | ---
`__cpp_lib_starts_ends_with` | `201711L` | (C++20) | String prefix and suffix checking: starts_with() and ends_with()

### Example

Run this code

    #include <cassert>
    #include <string_view>

    int main()
    {
        using namespace std::literals;

        assert
        (""
            // (1) starts_with( basic_string_view )
            && "https://cppreference.com"sv.starts_with("http"sv) == true
            && "https://cppreference.com"sv.starts_with("ftp"sv) == false

            // (2) starts_with( CharT )
            && "C++20"sv.starts_with('C') == true
            && "C++20"sv.starts_with('J') == false

            // (3) starts_with( const CharT* )
            && std::string_view("string_view").starts_with("string") == true
            && std::string_view("string_view").starts_with("String") == false
        );
    }

### See also

ends_with (C++20) | checks if the string view ends with the given suffix (public member function)
starts_with (C++20) | checks if the string starts with the given prefix (public member function of `std::basic_string<CharT,Traits,Allocator>`)
ends_with (C++20) | checks if the string ends with the given suffix (public member function of `std::basic_string<CharT,Traits,Allocator>`)
contains (C++23) | checks if the string contains the given substring or character (public member function of `std::basic_string<CharT,Traits,Allocator>`)
contains (C++23) | checks if the string view contains the given substring or character (public member function)
compare | compares two views (public member function)

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